The present invention relates to electric control apparatus for internal combustion engines and more particularly to a method and apparatus for electronically controlling an internal combustion engine by means of a microcomputer (MPU).
With the ever increasing demand for automobiles as popular means of transportation, various social problems have arisen. Included among these problems are mainly the polution of the atmosphere and the consumption of petroleum energy.
In spite of advances in engine control, efforts continue to be made for the control of exhaust gas. However, these attempts have resulted in a deterioration of the overall efficiency of an internal combustion engine (hereinafter referred to as an engine). From the standpoint of preventing the deterioration of the engine operating efficiency and improving the control of exhaust emissions, attempts have been made to use electronic controls and improve the control accuracy. For instance, electronically controlled fuel injection systems and ignition timing control apparatus have been proposed and various types of ignition timing control apparatus using a microcomputer have been proposed.
It has been the tendency of the previously known systems to replace the mechanical controls with corresponding electrical controls. As a result, electronic control systems have been proposed which are each associated with an individual one of the controlled systems.
To effect the control of exhaust emissions and ensure efficient operation of an engine, the engine must be controlled as a whole. By simply providing controlled systems each associated with a separate engine control as mentioned previously, there has been an insufficient organic interaction between the controlled systems and it has been difficult to provide a sophisticated control. There has been another disadvantage of requiring excessively complicated circuitry. In addition, a plurality of circuits have been required for detecting the irregularly introduced outputs of sensors including an angular position sensor, etc.
In U.S. Pat. No. 4,276,601 an engine control method and apparatus are disclosed which effect such complicated engine controls electronically and collectively in accordance with digital computational operations and its input/output circuit includes a large number of register groups into which are set the data processed by an MPU, such as, the values corresponding to ignition timings and fuel injection quantities, and this overall control requires large-scale circuitry thus making it difficult to integrate the required MPU and input/output circuit on the same semiconductor. Thus, there has been the disadvantage of the productivity being inferior.